1. Field of the Invention
This invention relates to safety systems for miners operating in an underground mine. More particularly, this invention relates to a toxic gas removal and air conditioning system for providing safe and breathable air to occupants of a miner survival chamber when the atmosphere outside the chamber contains potentially harmful gases.
2. Background Discussion
Events such as floods, nuclear radiation accidents, explosions, fires, chemical spills, terrorist toxic gas attacks, and many other such hazards, can require that humans in an affected area take refuge. Underground mines, in particular, present a host of such hazards. There are numerous risks inherent in underground mining operations: fires, cave-ins, methane or coal-dust explosions, flooding, asphyxiation, poisonous gasses in the mine atmosphere, and so forth.
When any person must seek refuge from the aftermath of an event such as those described above, most especially when miners are trapped underground, survival may depend upon the ability to find temporary shelter inside a survival refuge chamber until the danger has passed, or until rescue responders find and extract the miners from the chamber. Specially designed survival chambers are therefore typically placed at various locations in a mine, and miners are trained and drilled to know these locations almost reflexively. In this way, if a mine accident occurs, the miners can quickly find and enter the nearest survival chamber, where they can occupy the chamber until it is safe to exit.
Since survival chambers are air-sealed to prevent the intrusion of dangerous gasses that may be present in the mine atmosphere outside the chamber, the miners have only four possible sources of oxygen (O2). These include: (1) the O2 present in chamber air before it was sealed, which can include O2 found in compressed air tanks inside the chamber; and (2) the O2 that can be introduced into the chamber from another source outside the chamber, including O2 found in (a) air piped into the chamber from outside compressed air tanks; (b) the mine atmosphere immediately surrounding the chamber; and (c) air piped into the chamber from a source outside the mine.
The amount of time that a miner (or group of miners) can survive in a survival chamber depends, at least in part, on the amount of O2 available inside the chamber. Since the rescue operations may take days (even weeks), it is critically important that survivable O2 levels be present in the air inside the chamber for the longest period of time possible.
It is important to recognize that air inside a sealed chamber occupied by humans becomes contaminated over time, due primarily to the occupant exhalations that introduce additional carbon dioxide (CO2) and carbon monoxide (CO) into the chamber's atmosphere.
When the ratio of CO2 or CO to O2 is too large, the survival chamber occupants can suffer CO2 or CO poisoning. To prevent this condition, air-scrubbing systems are employed within the chamber to remove excess CO2 and CO from the chamber atmosphere. Such an air-scrubbing system must be intrinsically safe in a mine environment, meaning that it must not be able to generate unsafe conditions, such as generating a spark, or emitting an explosive or poisonous gas in sufficient quantity to present a danger. It must also be very rugged to ensure uninterrupted operations in the hostile environment characteristic of underground mines. Additionally, it must be capable of surviving the forces present inside the chamber when an explosion occurs outside the chamber. [For purposes of the instant application, “intrinsically safe” shall take the meaning set out in 30 CFR Pt. 18.2: “Intrinsically safe means incapable of releasing enough electrical or thermal energy under normal or abnormal conditions to cause ignition of a flammable mixture of methane or natural gas and air of the most easily ignitable composition.”]
Further, such a system would optimally detect loss of externally-supplied power, and automatically begin operation when such a condition is detected, so it is not necessary for miners to manually start or operate the air scrubber.
The noise generated by an air-scrubbing system should also be minimized. This is because miners occupying the survival chamber must listen to the noise for extended periods of time, and the psychological impact of this long-term exposure to the noise can be negative.
In order for a rescue team to verify that the air-scrubber system is operating (without entering the survival chamber), the air-scrubbing system should have a way to wirelessly communicate its condition to systems outside the chamber.
The current art does not provide satisfactory solutions to any of these problems, and the marketplace does not include any air-scrubbing systems for use in survival chambers in underground mines that meet all of these requirements. There is thus an urgent and critical need for such a system to significantly improve the ability of trapped miners to survive a catastrophic incident.